[Logic] 开关抖动及其处理办法（英文文档）

/* SoftwareDebounce

 * 

 * At each transition from LOW to HIGH or from HIGH to LOW 

 * the input signal is debounced by sampling across

 * multiple reads over several milli seconds.  The input

 * is not considered HIGH or LOW until the input signal 

 * has been sampled for at least "debounce_count" (10)

 * milliseconds in the new state.

 *

 * Notes:

 *   Adjust debounce_count to reflect the timescale 

 *     over which the input signal may bounce before

 *     becoming steady state

 *

 * Based on:

 *   http://www.arduino.cc/en/Tutorial/Debounce

 *

 * Jon Schlueter

 * 30 December 2008

 *

 * http://playground.arduino.cc/Learning/SoftwareDebounce

 */



int inPin = 7;         // the number of the input pin

int outPin = 13;       // the number of the output pin



int counter = 0;       // how many times we have seen new value

int reading;           // the current value read from the input pin

int current_state = LOW;    // the debounced input value



// the following variable is a long because the time, measured in milliseconds,

// will quickly become a bigger number than can be stored in an int.

long time = 0;         // the last time the output pin was sampled

int debounce_count = 10; // number of millis/samples to consider before declaring a debounced input



void setup()

{

  pinMode(inPin, INPUT);

  pinMode(outPin, OUTPUT);

  digitalWrite(outPin, current_state); // setup the Output LED for initial state

}





void loop()

{

  // If we have gone on to the next millisecond

  if(millis() != time)

  {

    reading = digitalRead(inPin);



    if(reading == current_state && counter > 0)

    {

      counter--;

    }

    if(reading != current_state)

    {

       counter++; 

    }

    // If the Input has shown the same value for long enough let's switch it

    if(counter >= debounce_count)

    {

      counter = 0;

      current_state = reading;

      digitalWrite(outPin, current_state);

    }

    time = millis();

  }

}

// INCLUDES

#include <stdio.h>

#include <stdlib.h>

#include <xc.h>



// CONFIG

#pragma config FOSC = INTOSCIO  // Oscillator Selection bits (INTOSC oscillator: I/O function on RA6/OSC2/CLKOUT pin, I/O function on RA7/OSC1/CLKIN)

#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)

#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)

#pragma config MCLRE = ON       // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is MCLR)

#pragma config BOREN = ON       // Brown-out Detect Enable bit (BOD enabled)

#pragma config LVP = ON         // Low-Voltage Programming Enable bit (RB4/PGM pin has PGM function, low-voltage programming enabled)

#pragma config CPD = OFF        // Data EE Memory Code Protection bit (Data memory code protection off)

#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)



// DEFINITIONS

#define _XTAL_FREQ 4000000

#define LED1 PORTBbits.RB3

#define LED2 PORTBbits.RB2

#define BTN PORTBbits.RB5



// VARIABLES

char BTN_pressed = 0;

char BTN_press = 0;

char BTN_release = 0;

char Bouncevalue = 500;



// MAIN PROGRAM

int main(int argc, char** argv) {

    // Comparators off

    CMCON = 0x07;

    

    // Port directions, RB5 input, the rest is output

    TRISA = 0b00000000;

    TRISB = 0b00100000;

    

    // Port state, all low

    PORTA = 0b00000000;

    PORTB = 0b00000000;

    

    // Starting with LED1 high and LED2 low

    LED1 = 1;

    LED2 = 0;

    

    while (1)

    {

        // If BTN is pressed 

        if (BTN == 1)

        {

            // Bouncing has started so increment BTN_press with 1, for each "high" bounce

            BTN_press++;

            // "reset" BTN_release

            BTN_release = 0;

            // If it bounces so much that BTN_press is greater than Bouncevalue

            // then button must be pressed

            if (BTN_press > Bouncevalue)

            {

                // This is initial value of BTN_pressed. 

                // If program gets here, button must be pressed

                if (BTN_pressed == 0)

                {

                    // Toggle the LEDs

                    LED1 ^= 1;

                    LED2 ^= 1;

                    // Setting BTN_pressed to 1, ensuring that we will 

                    // not enter this code block again

                    BTN_pressed = 1;

                }

                // LEDs toggled, set BTN_pressed to 0, so we can enter 

                // toggle code block again

                BTN_press = 0;

            }

        }

        else

        {

            // Increment the "low" in the bouncing

            BTN_release++;

            BTN_press = 0;

            // If BTN_release is greater than Bouncevalue, we do not have a

            // pressed button

            if (BTN_release > Bouncevalue)

            {

                BTN_pressed = 0;

                BTN_release = 0;

            }

        }

        

    }

    return (EXIT_SUCCESS);

}